Zinc-Rich Moisture-Cure Polyurethane Primer, Performance-Based

Zinc-Rich Moisture-Cure Polyurethane Primer

PAINT SPECIFICATION NO. 40 – Zinc-Rich Moisture-Cure Polyurethane Primer, Performance-Based

1. Scope
1.1 This specification contains performance requirements for an organic zinc-rich moisture-cure polyurethane primer with a thermoset binder. SSPC PS 12.00 describes this primer as a Type II B zinc-rich primer.

2. Description
2.1 This zinc-rich moisture-cure polyurethane primer is characterized by the presence of free polyisocyanate groups capable of reacting with atmospheric moisture in order to form a film. Either single or two-component packaging is acceptable. Zinc loading requirements are given in Section 4.2.1. Appendix A provides additional information for slip critical applications.

2.2 This primer is available in two Types. Type I formula­tions, applied over properly prepared carbon steel surfaces, are suitable for use on parts or structures exposed in Environ­mental Zones 1A–interior, normally dry; IB–exterior, normally dry; 2A–frequently wet by fresh water, excluding immersion, 2B–frequently wet by salt water, excluding immersion, and 3B–chemical exposure, neutral (with suitable topcoat). Type II formulations, applied over properly prepared carbon steel surfaces, are suitable for exposure in Environmental Zone 2C–fresh water immersion.  Type II primers meet the require­ments of Section 7.4 for fresh water immersion in addition to the requirements for Type I.

2.3 Primers described by this standard provide corrosion resistance and accept application of suitable topcoats. Unless a Type I primer is specified, the primer described by this standard is intended to comply with Type II requirements.

2.4 Polyurethane primer is intended for application by spray directly to a steel substrate, with the allowance for small area touch-up by brush (see Note 11.1).

3. Reference Standards
3.1 The latest issue, revision, or amendment of the refer­ence documents in effect on the date of invitation to bid shall govern unless otherwise specified. Those documents marked with an asterisk (*) are referenced only in the Notes or the Appendix, which are not requirements of this specification.

3.2. If there is a conflict between the requirements of any of the cited reference documents and this standard, the requirements of this standard shall prevail.

3.3 SSPC STANDARDS AND JOINT STANDARDS:

SSPC Guide 13	Guide for the Identification and Use of Industrial Coating Material in Computerized Product Databases
SP 1	Solvent Cleaning
SP 5/NACE No. 1	White Metal Blast Cleaning
PA	Measurement of Dry Coating Thickness with Magnetic Gages
PS 12.00	Guide to Zinc-Rich Coating Systems

3.4 ASTM INTERNATIONAL STANDARDS:1

A 572 Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Structural Steel
D 185 Standard Test Methods for Coarse Particles in Pigments, Pastes, and Paints
D 520 Standard Specification for Zinc Dust Pigment
* D 562 Standard Test Method for Consistency of Paints Measuring Krebs Unit (KU) Viscosity Using a Stormer-Type Viscometer
D 714 Standard Test Method for Evaluating Degree of Blistering of Paints
* D 1475 Standard Test Method for Density of Liquid Coatings, Inks, and Related Products
* D 1640 Standard Test Methods for Drying, Curing, or Film Formation of Organic Coatings at Room Temperature
D 1654 Standard Test Method for Evaluation of Painted or Coated Specimens Subjected to Corrosive Environments
* D 2369 Standard Test Method for Volatile Content of Coatings
* D 2371 Standard Test Method for Pigment Content of Solvent-Reducible Paints
D 2794 Standard Test Method for Resistance of Organic Coatings to the Effects of Rapid Deformation (Impact)
D 3278 Standard Test Methods for Flash Point of Liquids by Small Scale Closed-Cup Apparatus
D 4417 Standard Test Methods for Field Measurement of Surface Profile of Blast Cleaned Steel
D 4541 Standard Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers
D 5894 Standard Practice for Cyclic Salt Fog/UV Exposure of Painted Metal, (Alternating Exposures in a Fog/Dry Cabinet and a UV/Condensation Cabinet)
D 6580 Standard Test Method for the Determination of Metallic Zinc Content in Both Zinc Dust Pigment and in Cured Films of Zinc-Rich Coatings

3.5 FEDERAL SPECIFICATIONS AND STANDARDS:2

FED-STD 141 Paint, Varnish, Lacquer and Related Materials: Methods of Sampling, Inspection, and Testing
* Method 3011 Condition in Container
Method 4331 Spraying Properties

3.6 AMERICAN NATIONAL STANDARDS INSTITUTE (ANSI) STANDARD:3
ANSI Z129.1 Hazardous Industrial Chemicals–Precautionary Labeling

3.7 American Association of Highway and Transporta­tion Officials (AASHTO) Specification4

* Standard Specifications for Highway Bridges, Division 1, Section 10.32.3.2.3, Appendix A, Testing Method to Determine the Slip Coefficient for Coatings Used in Bolted Joints

4. Composition Requirements

4.1 The manufacturer is given wide latitude in the selection of materials and manufacturing processes.

4.2 PIGMENT REQUIREMENT

4.2.1 The major pigment component in polyurethane primer coating is zinc dust. The paint shall contain a minimum of 65% zinc dust pigment by weight in the dry film per ASTM D 6580 (see Notes 11.2 and 11.3).

4.2.2 Other optional pigment components include extenders, curing aids, tinting colors, and suspension and pot life control agents.

4.3 RESIN REQUIREMENT: The resin used in the coating shall be a polyisocyanate-based product that cures through a chemical reaction with atmospheric moisture. Use of other resins or modifiers shall be minimal and limited to products necessary for formula ingredient compatibility and to improve recoating properties. See Note 11.4 for information on modi­fying resins and Note 11.5 for information on volatile organic compound (VOC) content.

5. Standard Testing Conditions

5.1 TEST PANELS: The hot rolled steel test panels shall conform to ASTM A 572. Panel size shall be 100 mm x 150 mm x 3.2 mm (4 inch x 6 inch x 1/8 inch). Test panels shall be solvent cleaned in accordance with SSPC-SP 1 prior to blast cleaning. The test panels shall be blast cleaned in accordance with SSPC-SP 5. The blast profile shall be 44 to 57 micrometers (1.75 to 2.25 mils) as measured in accordance with ASTM D 4417, Method C.

5.2 APPLICATION: The primer shall be spray applied as a single coat in accordance with manufacturer’s written recommendations. The primer shall show no streaking, running, sagging, or other defects during application or while drying.

5.3 DRY FILM THICKNESS: The dry film thickness (DFT) on the test panels shall meet the manufacturer’s written recom­mended range. The DFT shall be measured in accordance with SSPC-PA 2, Appendix 5.

5.4 CURE: The primer shall be dried and cured in accor­dance with manufacturer’s written recommendations. Before any testing, all coated panels shall be aged for a minimum of 7 days in an environment with a minimum relative humidity of 55%, and at a temperature of 23 ± 2 °C (73.5 ± 3.5 °F).

5.5 SCRIBING:
Scribe two parallel lines on the face of the coated panels so as to expose the underlying metal before testing. The lines shall be at least 2.5 cm (1 inch) from the edge, the top, and the bottom of each panel and at least 5 cm (2 inches) from each other. Each scribe shall be 6 cm (2.4 inches) long. The scribes shall run vertically or at an angle across the face of the panel. Follow the scribe-making procedure described in ASTM D 1654.

5.6 BACKS AND EDGES: Coat and seal all edges and the back side of each panel with a coating or tape that will provide the necessary protection to these surfaces.

6. Requirements of Liquid Coating

6.1 MIXING: The liquid portion of a multi-component primer shall be mixed and dispersed to produce a product that is uniform, stable, free from grit, and in conformance with the requirements of this specification.

6.1.1 The pigment portion of a multi-component primer (if supplied as a dust) shall be dry and loosely packed prior to mixing.

6.1.2 The single-component primer shall be capable of being dispersed under mechanical agitation to a smooth, uniform consistency and shall not show any objectionable properties in the mix.

6.1.3 After mixing and filtering through a standard 60 mesh screen in accordance with ASTM D 185 the amount of coarse particles and skins retained shall not exceed 0.5% by weight (see Note 11.6).

6.2 STORAGE STABILITY: Neither the vehicle of the multicomponent coating nor the ready-mixed primer shall show thickening that is detrimental to performance or appli­cation properties. The components or primer shall exhibit no curdling, gelling, gassing, or hard caking after being stored unmixed for a minimum of six months from date of delivery in a tightly sealed, unopened container at a temperature of 10 to 32 °C (50 to 90 °F). The manufacturer shall also provide information on primer shelf life on the product data sheet as stated in SSPC-Guide 13, Section 4.4.11.

6.3 WORKING PROPERTIES: The mixed polyurethane primer coating shall spray easily and show no signs of, streaking, running, sagging, or other objectionable features when applied within the coating manufacturer’s recommended film thickness range, and tested in accordance with FED-STD 141, Method 4331. Note 11.7 provides additional information on material inspec­tion and quality assurance tests.

7. Laboratory Physical Tests of Applied Films

7.1 PRIMER ADHESION TO SUBSTRATE: Apply the primer to three panels in accordance with Sections 5.1 through 5.4. Test adhesion according to ASTM D 4541, Method II, III, IV, or V. Perform three pulls per panel.  The minimum adhesion value of the primer to the substrate for each pull shall be 4.1 MPa (600 psi). In the case of adhesive failure below 4.1 MPa (600 psi), the pull test shall be repeated.

7.2 TOPCOAT ADHESION: Prepare three panels in accordance with 5.1 through 5.3. Apply a topcoat and cure as recommended by the manufacturer. The thickness of the topcoat shall conform to the manufacturer’s recommendations. Perform three pulls per panel. The minimum adhesion value of each pull shall be 4.1 MPa (600 psi). In the case of adhesive failure below 4.1 MPa (600 psi), the pull test shall be repeated. Information on the recoat time (which varies with each formula­tion) shall be provided by the manufacturer.

7.3 DIRECT IMPACT RESISTANCE: The minimum impact resistance shall be 6.8 N•m (60 inch-lb) when measured in accordance with ASTM D 2794.

7.4 WATER IMMERSION (Type II primers only): This test is intended to evaluate the ability of the primer to protect the steel substrate in fresh water immersion service.

7.4.1 Description of Test: Prepare triplicate panels in accordance with Section 5. Completely immerse them in deionized water of conductivity no higher than 5 µS for one year. During this time the water shall be aerated.

7.4.2 Rust Evaluation: After the specified exposure time, each replicate panel shall have no rusting on the coated portion. Slight rusting in the scribe mark is permissible and resulting staining shall be ignored. Strips 6 mm (1/4 inch) wide along the edges of the panel shall be ignored.

7.4.3 Blister Evaluation: After the specified exposure time, there shall be no blistering of the coated portion.

7.4.4 Scribe Evaluation: After the specified exposure time, the maximum undercutting or rusting measured from the center of the scribe shall be no greater than 2 mm (3/32 in) when evaluated in accordance with ASTM D 1654 (a rating of 7).

8. Accelerated Laboratory Weathering Requirements

8.1 CYCLIC SALT SPRAY/UV/CONDENSATION CABINET: Triplicate panels prepared in accordance with Section 5 shall be exposed in a cyclic test cabinet in accordance with ASTM D 5894 for 5000 hours.

8.1.1 Rust Evaluation: After the specified exposure time, each replicate panel shall have no rusting of the coated portion (a rust rating of 10 per SSPC-VIS 2). Slight rusting in the scribe mark is permissible and resulting staining shall be ignored. Strips 6 mm (1/4 inch) wide along the edges of the panel shall be ignored.

8.1.2 Blister Evaluation: After the specified exposure time, there shall be no blistering of the coated portion (a rating of 10 per ASTM D 614).

8.1.3 Scribe Evaluation: After the specified exposure time, the undercutting from the center of the scribe, measured at any point along the scribe, shall be a maximum of 2 mm (3/32 inch) when evaluated in accordance with ASTM D 1654. Slight rusting in the scribe mark is permissible and resulting staining shall be ignored.

8.2 SLIP TEST: If slip testing is required, refer to Appendix A.1.

Table 1 provides a summary of performance require­ments.

9. Labeling

9.1 Labeling shall conform to ANSI Z129.1.

9.2 Technical data shall be provided for at least all data elements categorized as “essential” in SSPC-Guide 13.

10. Disclaimer

10.1 While every precaution is taken to ensure that all information furnished in SSPC standards and specifications is as accurate, complete, and useful as possible, SSPC cannot assume responsibility nor incur any obligation resulting from the use of any materials, coatings, or methods specified herein, or of the specification or standard itself.

10.2 This specification does not attempt to address problems concerning safety associated with its use. The user of this specification, as well as the user of all products or prac­tices described herein, is responsible for instituting appropriate health and safety practices and for ensuring compliance with all governmental regulations.

11. Notes

Notes are not requirements of this standard.

11.1 All zinc-rich coatings are preferably applied by spray, but may be brushed for small areas or to fill in irregularities. Brushing should be done with extreme caution to avoid zinc settlement. All zinc-rich materials may settle, and care should be taken to ensure they are thoroughly mixed before and during application. Thinning zinc-rich primers usually accelerates the rate of settling. Exercise caution during work stoppages to prevent settling of zinc in hoses and equipment.

11.2 Typically, many organic zinc-rich primers contain at least 80% zinc dust pigment by weight in the dry film.

11.3 LEAD LEVEL IN ZINC DUST: ASTM D 520 speci­fies three types of zinc dust for use as a pigment in coatings. Type I is a general grade in which no maximum level of lead is specified. Type II is a high-purity grade with a maximum lead level of 0.01% by weight. Type III is the highest purity grade, with a maximum lead level of 0.002% by weight. Any grade of zinc dust can be used in the zinc coatings covered by this specification. However, it is important to note that if Type I zinc is used, it is possible to exceed the permissible exposure limit (PEL) for lead when the products are removed by abrasive blasting. For additional information relating the lead content of the coating to worker exposure to lead during blasting see Gary L. Tinklenberg and Denise M. Doezema, “Health Concerns for Workers Using Zinc-Rich Coatings,” Journal of Protective Coatings and Linings, Vol. 15, No. 5 [May 1998], pp 36-46. In addition to lead, cadmium and other toxic metals may pose a health hazard. Placing overly restrictive requirements on some materials may result in the inability of manufacturers to produce products meeting this standard.

11.4 MODIFYING RESINS: Other resins or modifiers are typically less than 10% of total resin content.

11.5 VOC Content: Federal limits for VOCs in industrial maintenance coatings were published in 1998 and may be found at http://www.epa.gov/ttn/atw/183e/aim/aimpg.html#RULE. These limits apply to the coating at the time of application after thinning according to the manufacturer’s recommendations. Many state and local governments and/or air quality manage­ment areas have more stringent VOC regulations than those in the federal rule. Information on the VOC content of each container before mixing or thinning is found on the container label and in the manufacturer’s safety data sheet. The coating manufacturer’s product data sheet usually provides informa­tion on the total VOC content of a coating after mixing and any recommended thinning.

11.6 The contracting parties may agree upon alternate screen sizes for new technology coatings.

11.7 QUALITY ASSURANCE TESTS: If the user chooses, tests may be used to determine the acceptability of a lot or batch of a qualified coating. The quality assurance tests are used to determine whether the supplied products are of the same type and quality as those originally tested and certified for acceptance. The selected tests should accurately and rapidly measure the physical and chemical characteristics of the coating necessary to verify that the supplied material is substantially the same as the previously accepted material. All of the quality assurance tests should be performed on the originally submitted qualification sample. The results of these tests are used to establish pass/fail criteria for quality assur­ance testing of supplied products.

11.7.1 Establishing Quality Assurance Acceptance Criteria: Many ASTM test methods contain precision and bias statements. Specification developers should be cognizant of the fact that these statements exist. Quality assurance test criteria should not be more stringent than the inter-laboratory precision of the test methods used.

Where precision and bias data are not available for a given test method, determine the standard deviation of a minimum of five measurements taken on the originally tested and certi­fied material. The pass/fail criterion is that the measurement of the test sample falls within two standard deviations of the target value. The contracting parties should agree on a target value.

11.7.2 Recommended Quality Assurance Tests: Recom­mended quality assurance tests include but are not limited to, infrared analysis (ASTM D 2621), viscosity (ASTM D 562), weight per gallon (ASTM D 1475), total solids (ASTM D 2369), dry time (ASTM D 1640), percent pigment (ASTM D 2371), and condition in container (FED-STD-141, Method 3011).

APPENDIX A: SLIP TEST

A.1 Significance of Test: Corrosion resistance is enhanced if faying surfaces are coated. However, a minimum coefficient of friction is necessary for slip-critical connections.

A.2 Description of Test: Details for testing the coefficient of friction can be found in AASHTO Standard Specifications for Highway Bridges, Division 1, Section 10.32.3.2.3, Appendix A, “Testing Method to Determine the Slip Coefficient for Coatings Used in Bolted Joints.”

¹ ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959. Standards are available online at http://www.astm.org.

² FED STD 141 is available from http://assist.daps.dla.mil/online/start/ (or search for ‘assist’ through your web browser).

³ American National Standards Institute, 1819 L Street, NW, Suite 600, Washington, DC 20036. Standards are available online at www.ansi.org

⁴ American Association of State Highway and Transportation Officials, 444 North Capitol Street, NW, Suite 249, Washington DC 20001. Standards are available online at https://bookstore.transportation.org.

TABLE 1 PERFORMANCE REQUIREMENTS
TEST	NUMBER OF SPECIMENS	EXPOSURE TIME	RUST RATING, SSPC-VIS 2	BLISTER RATING, ASTM D 714	SCRIBE UNDERCUTTING, ASTM D 1654
Corrosion after exposure in Cyclic Accelerated Test Cabinet (ASTM D 5894)	3	5000 hours	All 10	All 10	Slight rust in scribe, max. undercutting 2 mm (rating of 7)

MINIMUM ACCEPTABLE RATING

TEST

Primer Adhesion	3 panels, 3 pulls per panel	—-	4.1 MPa (600 psi) for any pull	ASTM D 4541, Method II, III, IV or V
Topcoat Adhesion	3 panels, 3 pulls per panel	—-	4.1 MPa (600 psi) for any pull	ASTM D 4541, Method II, III, IV or V
Direct Impact Resistance	3	—-	68 N•m (60 inch-lb)	ASTM D 2794

Water Immersion (Type II only)	3	1 year	All 10	All 10	Deionized water with conductivity of less than 5 µs/cm
			Scribe undercutting less than 2 mm

Slip Test (optional)

See AASHTO Standard

0.5

AASHTO Standard Specification from Section 3.7

PAINT SPECIFICATION NO. 40 – Zinc-Rich Moisture-Cure Polyurethane Primer, Performance-Based